Torsional vibration isolating motor mounting system, mounting arrangement, assemblies including the same

ABSTRACT

Motor vibration isolating arrangements and systems using such arrangements are disclosed. In preferred arrangements, leaf spring mounting arms have low torsional spring constants and yet strength to withstand shipping and handling loads. The mounting member spring constants for axial, radial and tilting vibration modes are selected in specific forms so that the characteristic vibration transmissibility ratios for these modes are each close to unity, but so that torsional mode vibration transmissibility is substantially less than unity. In particularly preferred arrangements, sheet steel having a martensitic grain structure is utilized. In some forms, the motor shell constitutes one weldable member and a holding plate is weldable. The spring material is protected by heat sinking from being softening and weakened by conventional welding processes. The heat sinking members also contribute to a very strong fastening scheme.

CROSS REFERENCE TO RELATED APPLICATION

This application is a division of my now co-pending and allowedapplication Ser. No. 636,547 which was filed Dec. 1, 1975; now U.S. Pat.No. 4,063,060 issued Dec. 13, 1977 and the entire disclosure of which isspecifically incorporated herein by reference.

BACKGROUND OF THE INVENTION

The present invention relates generally to motor mounting systems, motormounting arrangements, assemblies including the same, and flexible arms;and particularly those that are adapted for interconnecting a motordirectly with a blower wheel and blower housing in a manner thatprovides improved isolation of torsional vibrations and yet alsounfailingly provides stringent control of axial and tilting motormovements without excessively amplifying vibrations associated with suchmovements.

In direct drive blower applications (for example those designed forfurnaces and in room air conditioning applications), many differentmotor vibration isolation schemes have been used in an effort to reducethe noise caused by vibrations transmitted from the motor to the blowerhousing and any associated connected duct work; or to a support in anair conditioner. Predominant single phase induction motor torsionalpulsations or vibrations having a frequency that is equal to or amultiple of twice the line frequency (for example 120 Hz for 60 Hz powersupplies and 100 Hz for 50 Hz power supplies) are usually the source ofthe most objectionable noise in both of the above-mentioned applicationsand an effective but inexpensive noise isolation scheme for thisvibration mode and frequencies is very much needed.

Blower wheels supported within blower housings typically are dimensionedand positioned so that relatively close running tolerances aremaintained between each wheel and housing in the interest of maximizingblower efficiency. In direct drive applications, a motor is suspendedfrom the blower housing scroll and the motor shaft in turn supports anddrives the blower wheel within the housing. This type of direct drivearrangement is very desirable because of its relative simplicity andeconomy as compared to other arrangements (e.g., those that requireseparated components such as belts, pulleys, separate blower wheelbearing systems and supports, etc.). However, with prior direct drivearrangements, it has been necessary to use complex and expensivemounting arms and related parts in order to generally satisfy therequisites of good torsional vibration isolation and acceptable controlof other motor movement.

It has long been known that motor vibrations or pulsations may beamplified during transmission to a blower housing, depending on thefrequency of vibration and resonant frequency of the mounting system (orparts thereof). Thus, the resonant frequency of each part of such systemshould be considered in designing a mounting arrangement. However,direct drive blower motors also must be supported with sufficientstiffness or rigidity to prevent sagging or drooping of the motor and toprevent blower assembly damage from "shipping shock" tests or duringactual shipping and handling. One primary problem exists because designefforts directed to minimizing the transmission of torsional modevibrations may well increase the transmission of (or chance ofamplification of) axial and tilting mode vibrations and may evenexcessively reduce the structural integrity of a given arrangementvis-a-vis shipping shock.

Generally speaking, it would be preferable to completely isolate axialmode and tilting mode motor vibrations from a blower housing in directdrive applications. However, the need to rigidly support the motor andblower wheel, and thus maintain a predetermined running clearancebetween blower parts, has not permitted the use of connections betweenthe motor and blower housing that are sufficiently "soft" to providesuch complete isolation.

Typical mobile home furnace blowers utilize motors rated atapproximately 373 watts (0.50 hp) or more and having a mass of 5.9 kg(13 pounds) or more. On the other hand, even heavier and more powerfulmotors often are used in typical residences, offices, and shop areasthat utilize air moving blowers. The larger mass of such motors requireseven more rigid mounting members for avoidance of tilting problems andshipping shock damage than would be the case with motors of smaller masssuch as those used, for example, for window fan applications (typicallythese motors are rated at 75 watts or less and have a mass of 2.2 kg orless).

Generally speaking, the larger the mass and power of the motor, the moredifficult it is to resolve the abovementioned problems; and solutionsapplicable to small motor applications are not always applicable toarrangements involving larger motors.

For example, many appliances that incorporate blower mounted motors aresubjected to mechanical tests that simulate "shipping shock"-- i.e.,conditions that might occur during handling and shipping of suchappliances. These conditions could be bouncing onto a truck loadingdock, rough railway transit, etc. The actual form of the tests may varyfor different appliance manufacturers and for different types ofappliances. However, one commonly used test procedure is spelled out ina test sequence specification of the "National Safe Transit Committee"(sponsored and coordinated by the Porcelain Enamel Institute, Inc.) forpackaged products of one hundred pounds or more. This sequence involvesvertically vibrating the packaged product for at least one hour at afrequency such that the product will momentarily leave the vibratingtable or platform during the vibration cycle; and then permittingmovement of the packaged product along an inclined plane until a face oredge of the package impacts against a backstop. This impact test may becarried out with a "Conbur Incline" testing device or other equipmentproducing equivalent results and a specified shock recorder. Of course,other tests may take place with an appliance unpackaged. In any event,however, after the selected test or test sequence, the appliance itself(e.g., a furnace) is inspected for damage, and such inspection usuallyinvolves close scrutiny of any electrical motors to determine that theshafts thereof and mountings therefor have not been deleteriouslyaffected.

Direct drive blower motors often are mounted so that the interfacebetween the mounting means and the blower housing is located along oradjacent to a curved inlet or eye of the blower housing, such curvedportion of the housing generally being less flexible and less apt to actas a sounding board for motor induced vibrations, and also being betterable to withstand shipping shock that might tend to tear the motor fromthe housing. It thus would be desirable that any improved arrangementsbe such that attachment to a blower would be along the curved inletthereof.

In the past, one approach for mounting motors directly to blowers hasinvolved the use of lugs that were fixed (for example by bolts or bywelding) to a motor frame. In some applications utilizing this approach,the lugs were fixed (for example by bolting or welding) directly to ablower housing or scroll without grommets; and in others grommets havebeen used. In still other blower applications, such lugs have beeninterconnected with the motor by means of a strap or band.

The general objectives of the mounting arrangements used heretofore havebeen to provide sufficient mounting rigidity to avoid excessive tiltingand axial movement of the motor during operation and to withstandshipping shock, while also attempting to minimize the transmission ofvibrations (particularly torsional mode vibrations) to the housingthrough the motor mounting members. Unfortunately, improvement of agiven design for one of these characteristics frequently will have anegative affect on the other characteristics. In addition, it hassometimes been necessary to provide "internal packaging" forarrangements that are good noise suppressors. For example, temporarysupplemental supports or pads may be provided in furnace blowers fortransit purposes. These supports or pads then are discarded prior toputting the furnace (or other appliance) in operation. Thus, engineeringcompromises must be made even with the complex known mountingarrangements.

A single member lug arm approach has long been recognized as apreferable form of direct drive motor mount (from a cost standpoint),but such approach simply has not been satisfactory in practice fordirect drive blower applications vis-a-vis good torsional mode vibrationisolation in combination with good mounting rigidity. For this reason,among others, it has been necessary to use relatively complex mountingarrangements for those applications where maximum isolation of torsionalmode noise was to be provided as well as sufficient structural strengthto meet shipping shock tests. For example, one prior arrangement hasrequired the use of costly resilient hubs or cushion ring isolatorsalong with a multitude of other different parts that have been assembledtogether to provide a costly and complex mounting arm assembly.

One or two member lug mounts have also been devised that have been usedwith ultra-soft or ultra-resilient blower mounting pads or grommets.This particular type of approach, however, can create or aggravate stillother problems such as those associated with: motor sag; reduced tiltingmode resonant frequency with the result that such frequencies would fallinto an amplification range; shipping and handling damage; andovercompression of the pads or grommets (due to the weight of themotor-blower wheel) accompanied with effective stiffening of such padsor grommets.

Although a number of different design and performance criteria have beendiscussed hereinabove as illustrative of the complexity of the factorsthat must be satisfied with direct drive motor mounting arrangements, itwill be understood that numerous other considerations may furtherconfound the search for a desirable solution to the direct-mounted motorproblems mentioned hereinabove. One of these, for example, is thepossibility that a given motor mounting arrangement might have tosupport a motor with its shaft vertical, horizontal, or at somespecified angle therebetween in different applications.

Single member types of mounting arms or members for axial air flow fanshave been shown in prior literature. For example, Anderson U.S. Pat. No.1,781,155 shows a motor that is supported by three substantially flatand straight supporting arms, the shaft of which supports a propellertype axial flow fan. Propeller or disc type fan mounting arrangementssomewhat similar to Anderson's are also shown in Seyfried U.S. Pat. No.1,873,343 and Goettl U.S. Pat. No. 2,615,620. In Seyfried, leather,canvas, spring steel, and brass arms are mentioned; and in Goettl,curved arms having arcuate motor embracing portions are illustrated.

Although it is desirable to utilize one piece mounting arms for directdrive blower motors, competitive economics would favor the permanentattachment of such arms to a motor shell during manufacture of themotor. However, for designs having very long arms, increased packagingcosts and shipping costs due to increased package volume can offset thecost savings associated with single arm construction. Furthermore, whilelengthy arms of the type shown by Seyfried, Anderson, etc. may be madefrom a choice of different materials (as described, for example, bySeyfried) and have satisfactory strength and torsional vibrationtransmissibility characteristics; prior attempts to utilize flat singlemember supports for direct drive blower motors have resulted in mountingarrangements having either unsatisfactory strength characteristics orunsatisfactory torsional vibration transmissibilities.

To be more explicit, it can be assumed that the arms of Goettl,Seyfried, or Anderson (referred to hereinabove) would have sufficientstrength to resist failure in either a tensile mode or buckling modewhen supporting a propeller fan motor of given mass during a particulartest. However, if those arms were shortened to permit mounting of thesame motor in a blower housing inlet, even though the arms would stillbe sufficiently strong to not tear or buckle, the torsional modevibration transmissibility of such arms would be objectionablyincreased. For example, an arm shortened from an effective radial extentof about 7.21 inches to an effective radial extent of about 2.2 incheswould have a substantially greater transmissibility vis-a-vis 120 hztorsional mode vibrations. On the other hand, if the shortened arms werethen further modified by being reduced in thickness and axial width inorder to obtain a low transmissibility for torsional vibrations, theirresistance to buckling would be reduced about 69%, and their resistanceto failure due to tensile stresses would be reduced about 88%.

Accordingly, it would be desirable to provide new and improved motormounting arrangements that include relatively short single membermounting arms, motors incorporating the same, and assemblies includingthe same that are low cost in terms of total material and total laborinvolved therewith, and yet that are at least satisfactory if notimproved in terms of noise isolation and structural reliability. Itwould also be desirable to provide such arrangements that could beeasily adapted for use with motors having different housingconfigurations or that are to be mounted with different shaftorientations; and systems including the same.

Accordingly, it is a general object of the present invention to providenew and improved motor mounting systems, motor mounting arrangements andsystems including the same whereby the above-mentioned and otherproblems may be solved.

It is a more particular object of the present invention to provide a newand improved motor mounting system, motor mounting arrangement, andsystems including the same, that has good resistance to shipping shockdamage even without supplemental or internal packaging, a high degree ofrigidity vis-a-vis axial and tilting mode vibrations, and lowtransmissibility for torsional mode vibrations.

It is a further object of the present invention to provide new andimproved motors and lug assemblies, that may be utilized to solve theabove-mentioned and other problems, and that may be quickly and easilyfastened to a blower or other type of housing.

SUMMARY OF THE INVENTION

In carrying out the above and other objects of the invention, in onepreferred form thereof, I provide a new and improved motor mountingarrangement which includes single member lugs specifically designed sothat the torsional mode resonant or natural frequency is less than twicethe frequency of the motor power supply divided by the square root oftwo (√2).

Illustrated mounting arrangements are very "soft" (i.e., they have a lowspring constant) with respect to torsional mode vibrations, are "stiff"with respect to axial and tilting mode vibrations, structurally reliableduring shipping shock tests, and yet are readily deflectable torsionallyfor easy assembly with a blower housing.

In specific forms illustrated herein, arrangements exemplifying theinvention include lugs that are flexible in the torsional direction butstrong and stiff in the axial and radial directions, thereby to preventsag or tilt of a direct driven blower wheel and to successfullywithstand shipping shock tests.

In more preferred forms that are illustrated herein, arrangementsembodying the invention include flexible members that are particularlyadapted for pivotal mounting on a blower housing, i.e., that areparticularly adapted to undergo at least limited oscillatory movementabout the longitudinal axis of a fastener which attaches a mountingportion of such members to a blower housing. In these forms, short butstrong mounting members are provided that also have low torsional modevibration transmissibilities because of the flexibility of or"springiness" of such members, and also because such vibrations areutilized to oscillate the members about their pivotal mountings.

The forms of the invention illustrated herein include flat mounting armsthat have low torsional spring constants and yet have sufficientstrength to withstand shipping and handling loads for motor and blowerassemblies, and to permit all angle motor mounting. These arms have aunitary motor mounting pad and unitary housing mounting means which area pad in one form and a tube in another.

The spring constants of the mounting members for axial, radial andtilting vibration modes are selected so that the characteristicvibration transmissibility ratios for these modes are each close tounity. However, the characteristic torsional mode vibrationtransmissibility is substantially less than unity. In particularlypreferred embodiments of the invention, high strength martensitic sheetsteel is utilized to form the mounting members.

In one approach that may be followed to produce systems and arrangementsembodying the invention, lug members are formed from the selectedmaterial and then one end of these members is trapped between oppositelyfacing surfaces of fastening members to provide additional strength. Insome forms, the motor shell constitutes one fastening member and aholding plate or pad is another fastening member. With these forms, itis preferred to capture the lug (e.g., with projections on one memberthat extend along cut-outs in the lug) against the motor shell and thenprojection weld the projections to the other member. This approach bothprotects the martensitic material from being softened and weakenedduring the welding process; and also provides a very strong fasteningscheme that meets the rigors of shipping and handling as well as therigors caused by prolonged vibration. The free end of the lug isspecifically configured to prevent deformation and tearing at the baseof the pad; and the lugs (even when fastened to a motor) are extremelyeasy to mount to a blower housing simply by deflecting the mounting arms(when necessary) with finger pressure so as to align holes in themounting arms with previously provided holes in the blower housing.

In accordance with another form of the invention, I trap the motor endof mounting arms between two pieces of steel that, when welded together,form a mounting block having a strap accommodating slot therein; andthen tie or strap the assembled blocks and members to a motor shell.

Important advantages are obtained by utilizing trapping means whenassembling mounting arms to motor shells or motor shell embracingligatures. For example, and in addition to preventing welding damage asreferred to above, the trapping means may be utilized to reinforce arelatively weak and small motor mounting tab. By this means, mountingarm dimensions may be minimized to further reduce the torsional modevibration transmissibilities thereof, even though the mounting tab forsuch an arm would likely be torn from the motor during shipping tests ifit were to be riveted, bolted, or welded directly to the motor shell.

Another important advantage of following yet another preferred procedureresides in reduced total assembly time and assembly procedurecomplexities. When carrying out this procedure, I support the shell andat least one reinforcing member, with a mounting arm tab sandwichedtherebetween, at a welding station. Projections then are welded to thereinforcing member and/or shell to permanently assemble the shell,mounting arm, and reinforcing member. The shell, mounting arm, and anyother parts assembled therewith then are treated (e.g., by phosphatizingand then painting) for appearance and corrosion or rust preventionpurposes. Subsequently, a rotatable member is assembled with the shellof a stator and supported within the shell to form a complete motor.

Generally the same procedures mentioned above may be followed whenriveting or bolting a mounting arm to the shell, with the rivets orthreaded fasteners (in lieu of welded projections) trapping the mountingarm tab between the motor shell and reinforcing means.

The subject matter which I regard as my invention is set forth in theappended claims. The invention itself, however, together with furtherobjects and advantages thereof may be better understood by referring tothe following more detailed description taken in conjunction with thedrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a somewhat schematic representation, with parts removed andparts broken away, of a motor-blower assembly embodying some of thefeatures of my invention;

FIG. 2 is a view taken along the line 2--2 in FIG. 1, it being notedthat arrows are used in FIGS. 1 and 2 to generally correspond withdifferent vibrational modes;

FIG. 3 is a plot of general transmissibility curves, withtransmissibility plotted versus the ratio of forcing frequency tonatural frequency for different damping factors; this figure beinguseful in explaining some of the benefits associated with utilization ofthe present invention;

FIG. 4 is a perspective view of the motor-blower assembly of FIGS. 1 and2;

FIG. 5 is an exploded perspective of parts of the structure shown inFIG. 4;

FIG. 6 is a side elevation of one mounting arm utilized in thearrangement of FIG. 3 and also shown attached to the motor of FIG. 2;

FIG. 7 is a view taken along line 7--7 of FIG. 6;

FIG. 8 is a view taken along line 8--8 of FIG. 6;

FIG. 9 is an exploded perspective view of portions of the structureshown in FIG. 3;

FIGS. 10 and 11 are sequential views that are useful in explaining onepreferred approach that may be followed when connecting a mounting armmotor pad or tab with a motor shell;

FIG. 12 is an enlarged view, with parts removed and parts in section,showing the mounting interface of the mounting arrangement of the motorand blower housing of FIG. 4;

FIG. 13 generally corresponds to FIG. 9 but illustrates a modifiedmotor-to-housing connection approach;

FIG. 14 illustrates a somewhat modified arrangement embodying featuresof the invention in another form thereof;

FIG. 15 is an enlarged view, with parts removed and parts in section, ofa portion of the structure shown in FIG. 14;

FIG. 16 is a view taken along the lines 16--16 in FIG. 15;

FIG. 17 is a side view of another arm useful in another embodiment ofthe invention;

FIG. 18 is a front view of the structure illustrated in FIG. 17;

FIG. 19 is an exploded perspective view of the mounting membersillustrated in FIGS. 17 and 18;

FIG. 20 is an elevation of another arm useful in another embodiment ofthe invention;

FIG. 21 is a view along lines 21--21 in FIG. 20;

FIG. 22 is a view along lines 22--22 in FIG. 20;

FIG. 23 is a schematic representation of vibratory movement that isuseful when describing what are believed to be vibratory movements ofstructures assembled according to one form;

FIG. 24 is a view somewhat similar to FIG. 20, and is useful whendescribing what are believed to be vibratory movements of structuresassembled according to another form;

FIGS. 25 and 26 are perspective views of a motor, and blower mountedmotor respectively according to one current but prior art approach; and

FIGS. 27 and 28 are perspective views of a motor, and blower mountedmotor respectively, according to another current but prior art approach.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In FIGS. 1 and 2, there is illustrated a motor mounting system thatincludes a combination of a blower housing 36, a blower wheel 37 coupledin direct drive relationship with the shaft 38 of a single phaseinduction motor 39, and three torsionally flexible mounting arms 41, 42,43.

It will be appreciated that the motor is directly mounted to the blowerhousing 36 along the curved scroll 44 which defines an air inlet 46 atone side of the housing, the housing also having a second air inlet 47co-axial with inlet 46 and the rotational axis 48 of motor 39.

Running clearances 49, 51 are provided between the blower wheel 37 andhousing 36, and these clearances must be maintained during operation.The amount of clearance may vary from one blower assembly to another,but generally is kept as small as manufacturing tolerances (and a givenmounting arrangement) will permit in order to minimize blower losses andthus maximize blower efficiencies.

Vibrations are inherently generated during operation of motor 39. Thesevibrations have different modes, and four different vibrational modeshave been denoted by arrows in FIGS. 1 and 2. With more specificreference to FIG. 2, the motor 37 tends to undergo an axial mode ofvibration and thus tends to oscillate in the direction of the arrow 52.In addition, motor 37 tends to vibrate radially as indicated by thearrow 53 and undergo tilting vibratory movement as represented by thearrow 54. For purposes of the present discussion, the tilting mode ofvibration of motor 37 may be considered to be a rocking type of movementabout the point 56. It will be understood, however, that radial andtilting mode vibrations may occur inplanes other than the vertical planeas represented in FIG. 2.

With reference now to FIG. 1, arrow 58 represents the vibratorydirection of movement of motor 39 due to torsional mode vibrations ofmotor 39 about its rotational axis 48 during operation thereof.

Since motor 39 is mounted directly to the blower housing, it will beappreciated that all of the various modes of vibration of the motor maybe transmitted directly to the housing 36. The housing 36, in turn, (andparticularly the face 59) may then act as a sounding board and mayamplify the vibrational sounds and noises transmitted thereto by themotor--depending on the transmissibility of the mounting arrangement forthe different vibrational modes. Moreover, these sounds may betransmitted directly through duct work connected to housing 36 or by theair mass being moved by the blower wheel 37.

Prior attempts (of which I am aware) at isolating motor inducedvibrations from a blower housing have been directed at minimizing aplurality of the four different vibrational modes represented in FIGS. 1and 2. However, it has long been known that some of the mostobjectionable noise transmitted to a blower housing are those vibrationsassociated with torsional mode vibrations. I have determined that goodresults can be obtained by minimizing the torsional mode resonantfrequency so as to minimize the torsional mode transmissibility, and byconcurrently increasing the resonant frequencies for modes of vibrationother than torsional in order to establish transmissibilities for thosemodes as close to unity as is practical. Preferred forms of physicalembodiments of the present invention discussed hereinbelow have beendevised with this approach in mind.

With reference to FIG. 2, it will be appreciated that whatever changesare made in the mounting arrangement there shown, the running tolerancesrepresented at 49 and 51 must be observed in order to avoid mechanicalinterference between the blower wheel and blower housing duringoperation. Unfortunately, some prior effects directed at minimizingtilting, axial, and radial vibration modes have permitted the motor tosag or droop and thus have reduced, if not eliminated, those clearances.

During shipping tests, the motor 31 will tend to move in at least thedirections indicated by the arrows 52, 53, and 54, depending upon howthe package is being tested. These forces are related to the mass of themotor 39 and will either tend to buckle the radially extending mountingmembers 41-43, or tend to cause failure in a tensile mode (for exampleby tearing one or more of these members from the blower housing ormotor, by stretching one or more of them, or by actually fracturing dueto tensile stresses).

Three curves 61, 62, and 63 are shown in FIG. 3. These curves arereferred to as general transmissibility curves and have been includedherein for purposes of discussion. These curves will be familiar topersons skilled in the art but, for those less skilled, a more thoroughunderstanding may be attained by referring to standard vibrationanalysis reference works. One such reference is a book entilted"Fundamentals of Vibration Analysis" by N. O. Myklestad, published bythe McGraw-Hill Book Company in 1956, and assigned Library of Congresscatalog number 55-11932.

Considering only curve 61 for the moment, FIG. 3 represents therelationship between the transmissibility (defined as the ratio of theamplitude of the transmitted force to the driving force) of a givenvibrating system to a ratio "r" which is defined as the ratio of theforcing frequency to the natural frequency of the system. If a systemwhere to have an infinitely great natural or resonant frequency, "r"would approach zero, and the transmissibility of such system would beone, so the amplitude of forces transmitted by the system would be thesame as the amplitude of the driving or exciting vibratory force. On theother hand, if the natural frequency of the system were an extremelysmall fraction of the forcing or driving frequency, the transmissibilitywould approach zero.

The knee in the curve 61 in the vicinity of r=1 is related to the amountof damping in the system and the curves 61, 62, and 63 are each drawnfor a different damping factor (this term is defined in the abovereferenced Myklestad book). More specifically, curve 61 is for a systemwhere the damping factor is equal to 0.4; curve 62 is plotted for adamping factor of 0.2; and curve 63 is plotted for a damping factor of0.1.

In preferred physical embodiments of the present invention, motorsupporting arrangements are designed so that the transmissibility ofmotor induced torsional mode vibrations to the blower housing is lessthan one and so that the ratio r is greater than √2.0. On the otherhand, these embodiments are designed so that the ratio r will be 0.3 orless for all vibrational modes other than torsional. Therefore, thetransmissibility of the mounting arrangement with regard to axial mode,radial mode, and tilting mode vibrations will be close to unity. Morespecifically, preferred systems are devised to have natural frequenciesin the axial, radial, and tilting modes that are at least 3 to 4 timesgreater than an expected fundamental forcing frequency so that the ratior of forcing frequency to natural frequency for the component mountingarms for these modes will be no more than about 0.3 but preferably evenless.

Turning now to FIGS. 4 and 5, the spatial and geometric proportions andrelationships of the blower housing 36, motor 39, and mounting arms41-43 will be described in more detail. It will be noted that in thepreferred forms illustrated in FIGS. 4 and 5, the motor ends 64-66 ofmounting arms 41-43 are tightly fixed to the housing or shell 60 of themotor 39 to prevent being torn from the motor during rough shipping orhandling (or tests simulating the same). The blower ends 71-73 of thearms 41-43 are fastened to the blower scroll 44 by means of self-tappingthreaded fasteners 76-78. It will be noted however, that other types offastening elements may be used.

As will be understood, a pair of motor leads 67, 68 are provided which,when connected across a source of excitation voltage, will causeoperation of the motor, it being noted that additional leads will beprovided for multi-speed operation. Moreover, a grounding lead 69 isconnected to the conductive housing of the motor and may be connected tothe blower housing itself or any other suitable grounded structure.

The fasteners 76-78 (see FIG. 4) are each tightened down against agrommet (such as the grommet 79) carried in an aperture in the blowerend of each mounting arm. Although the fastener is drawn down againstthe grommet so as to hold the motor 39 rigidly in place with respect tomovement in the tilting, axial, or radial modes; the blower ends ofblower mounting pads 71 of the arms 41-43 are held only loosely to theblower scroll 44 with respect to torsional mode movements.

It will be noted that each blower mounting pad 71 is offset relative tothe major, radially extending portion 81-83 of each mounting arm 41-43.Thus, the fastener accommodating aperture formed in the free or blowerends of the mounting arms is offset and each arm is capable ofoscillating or pivoting about its fastener. Therefore, the fasteners 78serve the purpose of holding the motor to the blower housing but alsoserve as pivot pins for the mounting arms.

Reference is now made to FIG. 23 which clearly reveals, in phantom, theoscillatory movement of mounting arm 41 in response to torsional modevibrations of motor 39 when it is mounted to the scroll 44 in the mannerdescribed hereinabove. It will be noted that the intermediate portion 81of mounting arm 41 is free to flex or bend in the manner of a leafspring. This flexing is further enhanced by the freedom of the pad 71 toundergo pivotal movement relative to the mounting axis 86.

With reference now to FIGS. 9 and 12, one means by which pivotalmovement of the illustrated mounting arms may be encouraged will bedescribed. FIG. 9 reveals stiff spacing means in the form of a steeleyelet or sleeve 87 which prevents gripping the mounting arm 41 sotightly with grommet 79 that arm 41 will not be free to pivot about theaxis 86 relative to the blower housing.

FIG. 12 shows that one portion of the grommet 79 cushions the pad 71 andprevents it from making direct metal to metal contact with the housing.Metal to metal contact between the pad 71 and either the eyelet portions88 or 91, 87 or screw 77 also is prevented by another portion of thesame grommet. Eyelet 87 includes a flange or shoulder 88 whichconveniently provides a bearing surface for the head 89 of screw 77 (ora washer positioned thereunder when desired). With the arrangementillustrated in FIG. 12, the fastener 77 may be drawn down very tightlyso that tubular portion 91 of eyelet 87 bears against scroll 44, and themotor thus is supported in a desired position without droop or sag.Moreover, with the arrangement illustrated in FIG. 12, the naturalfrequencies of the entire mounting system--vis-a-vis radial, tilting,and axial mode vibrations--will be very high with the result that atransmissibility approaching unity for each of these modes will beprovided, this being one of the above stated objectives of structuresembodying preferred forms of the invention.

The axial length of the tubular portion 91 of the eyelet is selected inconjunction with the height of the grommet 79 so that the grommet 79 isnot too tightly compressed in gripping relation with the blower pad 71even though screw 77 is drawn tightly against the eyelet 87. Thus,mounting arm 41 (as well as mounting arms 42 and 43 in FIG. 1) is ableto oscillate about axis 86 during operation.

Substantially improved results are obtained when mounting arrangementsare made pursuant to FIGS. 4-12 of the drawings herein. While thecombination of a leaf spring type single element mounting arm which ispivotal at its free end is important for obtaining the most desirableresults, other structural criteria must also be provided for in order toprovide an operative structure.

Test results have shown that, for one arrangement substantially as shownin FIGS. 9 and 12, the natural frequency of such arrangement fortorsional mode vibrations of 120 Hz is only about 26.6 Hz, which isquite desirable. On the other hand, when the grommet 79 was omitted forthe same arrangement, and pad 77 was bolted tightly to the blowerhousing as illustrated in FIG. 13, the torsional mode natural frequencyof the system for a forcing frequency of 120 Hz was about 33 Hz; and themotion of arm 41 was then (it is believed) as illustrated in FIG. 24.Although the vibration isolation characteristics of the FIG. 13arrangement were not as good as those of the FIG. 12 arrangement, theperformance of a FIG. 13 type of arrangement would still be sufficientfor many applications presently being served by more complex andexpensive prior art arrangements (e.g., by those of the type shown inFIGS. 25 and 26 herein).

For small effective radial lengths (i.e., where the effective radialdimension L in FIG. 6 was 2.2 inches), mounting arrangements usingmounting members configured exactly as shown in FIGS. 6-8 have failedduring testing. More specifically, conventional cold rolled steel andconventional spring steels simply have not had suitable physicalcharacteristics. However, short arms [i.e., arms with a length L ofabout 3.5 inches (8.9 cm) or less] can be made to perform satisfactorilywhen they are fabricated from martensitic steel. Martensitic steel, aswill be understood, is steel that has been specially processed totransform the microstructure of the material to martensite from, forexample, austenite. This type of steel typically will have a tensilestrength of from about 130,000 psi to at least about 220,000 psi. It hasnow been determined that such material having a tensile strength ofabout 140,000 psi or more is well suited for use in practicing thepresent invention. More expensive alloy steels and stainless steels mayalso be used, provided they have a martensitic microstructure, but theuse of such materials would represent a greater expense as compared tolow carbon, alloy free, martensitic cold rolled steel. This moreeconomical material is commercially available and may be purchased, forexample, from Inland Steel Co. Another source of relatively inexpensivemartensitic steel is the Athenia Steel Division, Division of theNational-Standard Co. of Clifton, N.J.

Review of FIG. 9 will quickly reveal that a better approach to utilizingthe invention is to stamp a mounting arm blank and form (i.e., "blend")the ends thereof to establish the motor mounting tab and housingmounting means. Since low carbon steels (e.g., 0.25% or less carbon)generally are more easily formed than higher carbon (e.g., 0.50% or morecarbon) steels, it is preferred to use a relatively low carbon steelsuch as that manufactured by Inland Steel Co. and marketed under thename "MartInsite" steel by that company.

If the arms 41-43 were proportionately larger so that the length "L"(see FIG. 6) were much longer (e.g., 10 inches), conventional coldrolled steel could almost certainly be used satisfactorily, but it isemphasized that the present invention is addressed to those problemapplications where short mounting arms must be used (e.g. where "L" isabout four inches or less).

Even when martensitic steel is utilized for lugs 41-43, other steps mustbe taken in order to ensure that the mounting arrangement issufficiently strong (even though only marginally so in some cases) tomeet the rigors of shipping tests. In order to provide the desired lowtorsional mode resonant frequencies that are needed, the arms 41-43 areformed of very thin material (e.g., about 0.035 of an inch or 0.9 mm);and the satisfactory attachment of such material to the shell of motor39 is difficult to accomplish. For example, direct welding of motorholding means such as pad 65 to motor shell 102 would be convenient andinexpensive. However, the heat associated with welding can cause anundesirable transformation of the martensitic microstructure of arm 41.This type of change would be accompanied by a reduction in strength, andfailure of arm 41 in the region of bend 156 or at the weld locationswould occur.

Thus, practical alternatives would be to utilize a structural adhesive,such as epoxy, to adhere pad 65 to shell 102, but care must be used toselect an adhesive of sufficient strength to withstand all testscontemplated; and the adhesive must be hardenable in a convenientlyshort period of time at temperatures that are not so high that theabove-mentioned martensitic microstructure is adversely affected.

Another approach would be to use large headed bolts or screws (orconventional bolts with washers to increase the bearing area thereof)which would pass through holes in tab 65 and thread into bosses formedin shell 102 (similar to boss 119 in FIGS. 9 and 12), or into nuts.While this approach should be satisfactory, it would not be aseconomical as the preferred approach now to be described in conjunctionwith FIGS. 9-11.

Initially, a mounting arm such as the arm 41 is positioned adjacent tothe outer periphery of the shell 102. Thereafter, and while the mountingarm is held in a desired position relative to the shell, a reinforcingstrap or plate 96 having a pair of projections 97, 98 thereon ispositioned over the motor mounting pad. Locating means (shown asapertues 101 in FIGS. 9-11) are defined by the motor mounting tab 65;and the projections 97, 98 co-operate with such locating means topermanently hold the mounting arm 41 in a fixed location on the shell102. When the shell is about 0.050 inch thick, and tab 65 is about 0.035of an inch thick, the plate 98 preferably is about 0.090 inch thick.This thickness of strap 96 prevents it from subsequently bending orbuckling and also provides a mass that co-operates with the mass ofshell 102 to provide heat sink means or heat transfer means that (it isbelieved) prevent adverse heat build-up and microstructure changes inthe tab 65.

One Preferred mode of carrying out the invention includes positioning amounting arm (e.g., arm 41) adjacent to a motor shell, positioning areinforcing plate adjacent to the mounting arm, and positioningprojection means so that the projection means interfit with locatingmeans defined by the tab 65 of the mounting arm. Thereafter, a weldingelectrode is relatively positioned adjacent to one side of the motorshell 102 and a second welding electrode is positioned adjacent to thereinforcing plate; and current is passed through the welding plate,projections, and the interface between the projections and the shellwhile the parts being welded are urged together so as to accomplish aweld along such interface (as best illustrated at 103, 104 in FIG. 11),and heat is transferred to the heat sink means to prevent substantialdegradation of the microstructure of the tab 65.

While round apertures 101 have been shown, it will be appreciated thatnotches rather than holes could be provided along the edges 104, 106 ofthe motor mounting pad 65. Other alternative arrangements of locatingmeans will readily suggest themselves to persons skilled in the art and,accordingly, the forms illustrated herein should be considered forpurposes of exemplification rather than limitation.

My investigations have revealed that mounting arrangements retaining thesuitable properties and characteristics mentioned above may also beprovided even though parts thereof are not permanently fixed to themotor shell itself. For example, the arrangements shown in FIGS. 14-16reveal that the invention may also be embodied in arrangements wherein areinforcing plate 107 (including projections) that is substantiallyidentical to the plate 96 may be welded to a notched backing or supportplate 103, with the motor end or pad 112 of the mounting arm 108permanently trapped therebetween. The mounting arm 108 is virtuallyindentical to the mounting arm 41 described hereinabove and thereforefurther details thereof are not described herein. It is noted, however,that plate 103 and plate 107 constitute heat sink means for the FIG. 15embodiment; and that projections on plate 107 (or plate 103) tend toconcentrate and localize welding heat in the same manner as projections97, 98 of FIG. 10. The band 109 is, as shown in FIG. 14, clamped about amotor 111.

In a preferred mode of assembly, the plate 107 is positioned so thatprojection means thereon trap locating means in the mounting pad 112against plate 103. Thereafter, one electrode is positioned above theplate 107 and another below the plate 103 whereupon the projections arewelded to the other plate to permanently trap arm 112 and define aligature accommodating notch or aperture 113. The ligature (such asstrap 109) is then threaded through such notch, and thereafter fastenedabout a motor.

Turning now to FIGS. 17-19, another embodiment of the invention will bedescribed. In the structure there shown, a mounting arm 126 is providedwith a motor pad 127 which has locating means 128, 129 (again in theform of apertures) that are used in conjunction with fastening themounting arm to a motor or other structure. Rather than utilizing a flatoffset blower pad, the blower end of the arm 126 is rolled into atubular shape and welded upon itself at 132. Thereafter, a spacer sleeve133, two washers 134, 136, and rubber or other resilient materialgrommets 137, 138 are assembled therewith. Thereafter, a bolt, screw, orother suitable fastener is inserted through the center of the spacersleeve to fasten the mounting arm to a blower housing. With thearrangement just described, the blower end of arm 126 is free to pivotabout such fastener even though it is not offset in the manner describedhereinabove in connection with FIG. 20.

It will be noted that welding (at 132) of the martensitic materialutilized for the arm 126 has just been indicated. Even though weldingmay alter the desirable martensitic characteristics of that portion ofthe arm 126 in the vicinity of the weld, the mounting arm still seemssuitable for use because (it is believed) any changes in martensiticmicrostructure are probably localized near the location of weld 132 andthis region of arm 126 is not subjected to as great a stress as thatportion closer to tab 127.

In FIGS. 20-22 three different elevations of a torsionally flexiblemounting arm 161 have been shown. The arm 161 includes a blower end tab162 and motor tab 163 with projection accommodating apertures 164, 166therein. The tab 162 also has a hole 167 therein which can be used toaccommodate a rubber grommet like the grommet 79 (of FIG. 12). Three ormore arms 161 may be used in lieu of arms 41-43 and these shorter arms161 are of particular benefit for double shaft motor applications (suchas room air conditioners) where the arm 161 would be fastened at theextreme end of a shell and mount the motor to a compartment wall ratherthan the eye of a blower.

Prior to the present invention, many attempts have been made to providedirect mounted motors that would have suitable vibrationtransmissibility characteristics. Even though many efforts have beenmade in this direction, and much patented literature is availableillustrating such efforts, two arrangements with which I am familiarthat have most closely approached the desired characteristics areillustrated as prior art in FIGS. 25-28.

FIGS. 27 and 28 illustrate a rather complex mounting structure which isassembled from a plurality of parts and fastened to a motor 174 by meansof resilient end rings or hubs 175 that are carried by the motor endframes 176. The bracket assembly 177 then is mounted to a blower housing178 by means of a number of bolts 179, all as illustrated in FIG. 28.The performance of structures illustrated in FIGS. 27, 28 has beenadopted by many persons in the industry as a standard of reference forgood vibration isolation systems, and many in the industry have utilizedthe arrangement shown in FIG. 28. However, this approach is expensive,and in this regard it will be noted that a number of different arms 180,181, 182 must be fabricated and then assembled with rings 175. Inaddition, a considerable amount of time and labor is involved inactually assembling this supporting structure 177 with the motor 174.

A somewhat less expensive approach is illustrated in FIGS. 25 and 26wherein a wire type cage 183 is fabricated and then clamped withligature means 184 to the outer periphery 185 of a motor 186. Relativelylarge resilient grommets or cushions 187 are then used to trap the endsof arm portions of the wire cage, and screws 189 are used to hold theentire structure on a blower housing 190.

Surprisingly, arrangements embodying the present invention yieldperformance characteristics and overall noise transmission qualitiesthat generally are as good, if not better in at least one respect foreach given design, than the best state of the prior art direct drivemotor mounting arrangements of which I am aware--including those ofFIGS. 25-28. In addition to having surprisingly good performance,arrangements embodying the present invention can now be made atsubstantially less cost than the prior suitable arrangements.Accordingly, substantial benefits can result from use of the presentinvention.

Accordingly, while I have now shown and described preferred andalternate embodiments of mounting arrangements, and methods of makingthe same (as well as components thereof); the disclosure containedherein should be construed as being exemplary, and the invention itselfshould be limited only by the scope of the claims that are appendedhereto and that form part of my disclosure.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:
 1. A torsional mode vibration isolating motor mounting systemfor an electric motor having a longitudinally extending shaft defining alongitudinally extending rotational axis and a stationary housing andadapted to be supported by a mounting surface, the system comprising: aplurality of mounting arms attached to the housing at circumferentiallyspaced apart locations and projecting generally radially from thehousing relative to the rotational axis; each of said mounting armscomprising a flat sheet material member having a motor holding tabformed as a unitary part thereof and bent to extend from a firstextremity thereof; each of said mounting arms further comprising amounting portion formed as a unitary part thereof at a second extremitythereof; each said mounting portion comprising means for promotingflexing movement of each arm in response to torsional vibrations andfurther comprising means for accommodating at least one resilient memberwith which each arm may be attached to a mounting surface for pivotalmovement of each such arm relative to said mounting surface; the portionof each arm between the extremities thereof comprising a flat flexiblearm portion having a width and preselected thickness less than saidwidth; each said flexible arm portion being generally rectangular incross-section in the central portion thereof and having the preselectedthickness thereof oriented, along the entire extent thereof between themounting portion and motor holding tab, in a direction generallytransversely relative to the rotational axis; and wherein the means foraccommodating at least one resilient member includes a fasteneraccommodating aperture for facilitating fastening of each of said armdirectly to a mounting surface.
 2. A torsionally flexible torsionalvibration isolation electric motor mounting arrangement for mounting amotor supporting structure, the arrangement comprising first and secondweldable members that cooperate as heat sink means with at least one ofsaid members including at least one weldable projection, and at leastone flexible mounting arm having a motor end with projectionaccommodating means therein and an end for connection to the motorsupporting structure; said motor end of the at least one flexible armbeing trapped between the first and second weldable members with theprojection accommodating means of said motor end accommodating said atleast one weldable projection, and wherein the first and second weldablemembers are welded together, whereby at least one of the weldablemembers provides an effective heat sink relative to the trapped motorend.
 3. The invention of claim 2 wherein the two weldable members form awelded block, and the welded block defines a ligature accommodatingregion.
 4. The invention of claim 2 wherein one of the members is amotor housing and the at least one projection is welded to the motorhousing.
 5. The invention of claim 2 wherein the at least one projectionis welded to a clamping member.
 6. The invention of claim 5 wherein theclamping member is arranged to be held fast to a motor housing by aligature.
 7. The invention of claim 6 wherein the ligature providesmeans for removably assembling the arm and a motor housing.
 8. Theinvention of claim 3 wherein at least the weldable member having aweldable projection is sized and proportioned to establish an effectivesink for heat associated with welding the projection, whereby such heatdoes not adversely affect the martensitic microstructure strengthcharacteristics of the flexible arm.
 9. The invention of claim 2 whereinthe mounting arrangement is combined with an electric motor having amotor housing and wherein said housing forms one of said weldablemembers.
 10. The invention of claim 9 wherein said at least one arm isformed from steel sheet having a martensitic microstructure.
 11. Theinvention of claim 9 wherein the arrangement includes at least threemotor supporting arms.
 12. A torsionally flexible torsional vibrationisolation electric motor mounting arrangement comprising first andsecond weldable members that cooperate as heat sink means with at leastone of said members including at least one weldable projection, and atleast one flexible mounting arm having a motor end with projectionaccommodating means therein; said motor end of the at least one flexiblearm being trapped between the first and second weldable members with theprojection accommodating means of said motor end accommodating said atleast one weldable projection; wherein the first and second weldablemembers are welded together, whereby at least one of the weldablemembers provides an effective heat sink relative to the trapped motorend; and wherein the at least one flexible arm is formed of a materialhaving a martensitic microstructure and wherein the at least oneweldable projection of said one of said members is welded to the otherone of said weldable members; said at least one weldable projectioncomprising means for localizing welding heat whereby such heat does notmaterially adversely affect the martensitic microstructure strengthcharacteristics of the flexible arm.
 13. In an assembly including ablower wheel, electric motor, and blower housing wherein the motor has arotatable member and stationary frame means, the blower wheel isfastened to the rotatable member of the motor for rotation therewith,and torsionally flexible means mount the motor directly to the blowerhousing, the improvement comprising: said torsionally flexible meansincluding at least one flexible arm having a motor pad rigidly connectedwith the frame means to prevent relative movement therebetween and saidflexible arm also having an end pivotally connected to the blowerhousing; said flexible arm being torsionally flexible relative to themotor during motor operation; and said flexible arm further being bothtorsionally flexible and pivotable about an axis along a mountinglocation in the blower housing during motor operation.
 14. The inventionof claim 13 wherein said flexible arm includes a flat portion unitarywith an end portion that is bent relative thereto; the bent end portionhas an aperture associated therewith; a fastener is disposed along theaperture and holds the arm to the housing; said flexible arm has a flatconfiguration along substantially the entire extent thereof between thebent portion and the motor mounting end; and said aperture is offsetfrom the plane of the flat portion.
 15. In an assembly including ablower wheel, electric motor, and blower housing wherein the motor has arotatable member and stationary frame means, the blower wheel isfastened to the rotatable member of the motor for rotation therewith,and torsionally flexible means mount the motor directly to the blowerhousing, the improvement comprising: said torsionally flexible meansincluding at least one flexible arm having a motor pad rigidly connectedwith the frame means to prevent relative movement therebetween and saidflexible arm also having an end pivotally connected to the blowerhousing; said flexible arm being torsionally flexible relative to themotor during motor operation, and said flexible arm further being bothtorsionally flexible and pivotable about an axis along a mountinglocation in the blower housing during motor operation; said flexible armincluding a flat portion unitary with an end portion that is bentrelative thereto and that has an aperture associated therewith; afastener disposed along the aperture and holding the arm to the housing;said flexible arm having a flat configuration along substantially theentire extent thereof between the end portion that is bent and the motormounting end; said aperture being offset from the plane of the flatportion; a resilient grommet disposed in the aperture in the bentportion of the arm; fastener means extending along the aperture andholding the bent portion of the arm to the blower housing; andstiffening means disposed along the grommet thereby to contribute to theaxial stiffness of the mounting arrangement and prevent unduecompression of the grommet while the arm is held to the blower housing,whereby oscillatory movement of the arm relative to the blower housingis permitted.
 16. The invention of claim 13 wherein the end of the armadjacent the housing is rolled upon itself; the rolled portion of thearm defines a fastener accommodating passageway; and fastener means areaccommodated by the passageway.
 17. The invention of claim 13 whereinthe flat arm is comprised of steel having martensitic strengthcharacteristics.
 18. A torsional mode vibration isolating motor mountingarrangement for an electric motor having a longitudinally extendingshaft defining a longitudianlly extending rotational axis and astationary housing and adapted to be supported by a mounting surface,the arrangement comprising: a plurality of mounting arms adapted to beheld in fixed position relative to the housing at circumferentiallyspaced apart locations and projecting generally radially from thehousing relative to the rotational axis; each of said mounting armscomprising a flat sheet material member having a motor tab formed as aunitary part thereof and bent to extend from a first extremity thereof;each of said mounting arms further comprising a mounting portion formedas a unitary part thereof at a second extremity thereof; each saidmounting portion comprising means for promoting flexing movement of eacharm in response to torsional vibrations and further comprising means foraccommodating at least one resilient member with which each arm may beattached to a mounting surface for pivotal movement of each such armrelative to such mounting surface; the portion of each arm between theextremities thereof comprising a flat flexible arm portion having awidth and preselected thickness less than said width; each said flexiblearm portion being generally rectangular in cross-section in the centralportion thereof and having the preselected thickness thereof oriented,along the entire extent thereof between the mounting portion and motortab, so that it will extend in a direction generally transverselyrelative to the rotational axis; and wherein the means for accommodatingat least one resilient member includes a fastener accommodating aperturefor facilitating fastening of each of said arms directly to a mountingsurface.
 19. In an assembly including air moving means, an electricmotor, and a motor support wherein the motor has a rotatable member andstationary frame means, the air moving means is fastened to therotatable member of the motor for rotation therewith, and torsionallyflexible means mount the motor directly to the motor support, theimprovement comprising: said torsionally flexible means including atleast one flexible arm having a motor mounting end interconnected withthe frame means to prevent relative movement therebetween and saidflexible arm also having an end pivotally connected to the motorsupport; said flexible arm being torsionally flexible relative to themotor during motor operation; and said flexible arm further being bothtorsionally flexible and pivotable about an axis along a mountinglocation on the motor support during motor operation.
 20. The inventionof claim 19 wherein said flexible arm includes a flat portion unitarywith an end portion that is bent relative thereto; the bent end portionhas an aperture associated therewith; a fastener is disposed along theaperture and holds the arm to the housing; said flexible arm has a flatconfiguration along substantially the entire extent thereof between thebent portion and the motor mounting end; and said aperture is offsetfrom the plane of the flat portion.
 21. The invention of claim 20further comprising: a resilient grommet disposed in the aperture in thebent portion of the arm; fastener means extending along the aperture andholding the bent portion of the arm to the motor support; and stiffeningmeans disposed along the grommet thereby to contribute to the axialstiffness of the mounting arrangement and prevent undue compression ofthe grommet while the arm is held to the motor support, wherebyoscillatory movement of the arm relative to the motor support ispermitted.
 22. The invention of claim 19 wherein the end of the armadjacent the motor support is rolled upon itself; the rolled portion ofthe arm defines a fastener accommodating passageway; and fastener meansare accommodated by the passageway.
 23. A torsionally flexible torsionalvibration isolation electric motor mounting arrangement comprising firstand second weldable members that cooperate as heat sink means with atleast one of said members including at least one weldable projection,and at least one flexible mounting arm having a motor end withprojection accommodating means therein; said motor end of the at leastone flexible arm being trapped between the first and second weldablemembers with the projection accommodating means of said motor endaccommodating said at least one weldable projection; wherein the firstand second weldable members are welded together, whereby at least one ofthe weldable members provides an effective heat sink relative to thetrapped motor end; and wherein the at least one flexible arm is formedof a material having a martensitic microstructure and wherein at leastone of said weldable members is sized and proportioned to provide aneffective sink for heat associated with welding the at least oneweldable projection whereby the martensitic microstructure andassociated strength characteristics of the at least one flexible arm aremaintained notwithstanding the heat associated with welding the at leastone weldable projection.
 24. A torsionally flexible torsional vibrationisolation electric motor mounting arrangement comprising first andsecond weldable members that cooperate as heat sink means with at leastone of said members including at least one weldable projection, and atleast one flexible mounting arm having a motor end with projectionaccommodating means therein; said motor end of the at least one flexiblearm being trapped between the first and second weldable members with theprojection accommodating means of said motor end accommodating said atleast one weldable projection; wherein the first and second weldablemembers are welded together, whereby at least one of the weldablemembers provides an effective heat sink relative to the trapped motorend; and wherein the flexible arm is made from a spring steel having apredetermined first thickness, the first weldable member is made from amaterial of a predetermined second thickness, and the ratio of thesecond thickness to the first thickness is at least about the numericalratio of 0.09 to 0.035, whereby the first weldable member exhibits heatsink attributes relative to the flexible arm.
 25. A torsionally flexibletorsional vibration isolation electric motor mounting arrangementcomprising first and second weldable members that cooperate as heat sinkmeans with at least one of said members including at least one weldableprojection, and at least one flexible mounting arm having a motor endwith projection accommodating means therein; said motor end of the atleast one flexible arm being trapped between the first and secondweldable members with the projection accommodating means of said motorend accommodating said at least one weldable projection; wherein thefirst and second weldable members are welded together, whereby at leastone of the weldable members provides an effective heat sink relative tothe trapped motor end; wherein the flexible arm is made from a springsteel having a predetermined first thickness, the first weldable memberis made from a material of a predetermined second thickness, and theratio of the second thickness to the first thickness is at least aboutthe numerical ratio of 0.09 to 0.035, whereby the first weldable memberexhibits heat sink attributes relative to the flexible arm; and whereinthe other weldable member has a predetermined third thickness, and theratio of the third thickness to the first thickness is at least aboutthe numerical ratio of 0.05 to 0.035.